1. Field
The present invention relates to a multiple throttle device that is connected to intake ports of an engine and controls volumes of air to be supplied to the intake ports. Particularly, the present invention relates to a multiple throttle device connected to a V-type engine having four or more cylinders.
2. Description of the Related Art
As the displacement of a vehicle engine and the number of cylinders thereof are being increased, a V-type engine is frequently adopted as the vehicle engine from viewpoints of a mounting space and weight reduction thereof.
When a body of the engine becomes compact, naturally, a requirement for also downsizing the respective instruments fixed to the engine body is increased. Among the instruments, a throttle device occupies a major position. In particular, in a motorcycle engine, a large restriction is imposed on a mounting space of the throttle device. Accordingly, it is beneficial that the throttle device be downsized as well as the engine body.
In recent years, an electronic control system has been adopted in place of the conventional carburetor system in the motorcycle. With regard to throttle valves of throttle bodies, a rotation angle of a throttle shaft is controlled by a throttle position sensor (TPS), and the throttle shaft is driven by a direct current (DC) motor. In the case where the number of throttle shafts is two as in the V-type engine, two DC motors are used. In general, it is necessary to adjust (hereinafter, simply referred to as “synchronize”) openings of the throttle valves in order to properly set rotation of the engine at the time of idling. Such synchronization is performed by a synchronization mechanism that rotates the throttle shaft. However, in the case where the number of throttle shafts is two as in the V-type engine, when the synchronization is performed for each of the throttle shafts, the throttle shafts may go out of mutual synchronization and turn into different synchronization states. Accordingly, for the purpose of preventing such a synchronization shift, a configuration is disclosed, in which two throttle shafts are link-coupled to each other by a joint rod, and the synchronization in one of the throttle shafts is reflected on the other throttle shaft as disclosed in Japanese Patent Application Laid-open No: 2004-239234.
However, in a configuration of driving such a multiple throttle device by the plurality of DC motors, weight of an entire apparatus is increased. Further, from the viewpoint of an installing space and cost of the DC motors, it is preferred that the DC motors be combined into one unit. Further, in the case where multiple DC motors are used, it is necessary to synchronize not only the throttle shafts with each other but also motions of the DC motors themselves with each other, and there is a problem that it is difficult to accurately synchronize the motions of the DC motors with each other. With regard to the synchronization between the throttle shafts, the two throttle shafts may be link-coupled to each other by the joint rod as in JP 2004-239234 A. However, such a structure should be avoided from a viewpoint of preventing vibrations, a viewpoint that the synchronization is prone to be shifted owing to an external impact, and the like.